The complex mechanisms associated with viral oncogenesis requires a broad understanding of aspects of virology, molecular and cellular biology, and immunology. It has been stated that viruses are among the strongest carcinogens known. These viruses include hepatitis B virus, hepatitis C virus and certain human papillomaviruses. In addition, certain human herpesviruses as well as retroviruses have been associated with certain cancers. The trainers within the proposed training grant direct productive and well-funded research programs that focus on four of the five above virus groups, which include hepatitis B virus, human papillomaviruses, herpesviruses, and retroviruses. This training grant application is a competitive renewal for years 16-20 of a program to support graduate students and postdoctoral fellows who are associated with a long-standing training program in virology and immunology. The trainers associated with the proposed program have their primary academic appointments within the Departments of Microbiology and Immunology, Medicine, Pathology, or Pediatrics. Each of the trainers directs a well-funded and productive research program in areas of virology and immunology. Although the trainers and trainees are primarily associated with the Department of Microbiology and Immunology, predoctoral students are also associated with multiple interdisciplinary graduate programs that cross departmental boundaries. A strength of the program is the numerous opportunities for interactions among the trainers, which contributes to the development of a highly supportive and interactive environment in which the trainees can reach their full potential as young scientists. The breadth of the scientific interests of members of the training faculty provides a blend of research areas within aspects of virology and immunology that allows the potential for outstanding training environment. The training program is further enhanced by numerous seminars, journal clubs, symposia, and special experiences that enhance the cancer training environment. The establishment, growth, and association with the Penn State Hershey Cancer Institute have enhanced the training environment for young scientists with an interest in cancer. The research accomplishments of the faculty, their strong commitment for training, availability of excellent core support facilities, and opportunities for extensive interactions all provide a dynamic training environment for the graduate students and postdoctoral fellows within the Viruses and Cancer training program.